What is the total length, in feet, of the actual walkway?

we know the trapezoids are similar, so that means all sides are at a ratio, thus
[tex]\bf \cfrac{model}{actual}\qquad \cfrac{AB}{EF}\implies \cfrac{6}{72}\implies \cfrac{1}{12}[/tex]
that means from the model to actual, the scale is 1:12, so the large side is 12 times as large.
so for the large trapezoid
EF = 6 * 12 =... 72
EH = 4 * 12 =.. 48
HG = 3 * 12 = ..36
GF = 3 * 12 =...36
72+48+36+36 = 192.